unit 17 情态助动词.ppt

* Unit 17 情态助动词 modal verbs 1.--Is John coming by train? --He should, but he ____ not. He likes driving his car. A. must B. can C. need D. may 2.It has been announced that candidates(候选人) ____ remain in their seats until all the papers have been collected. A. can B.will C. may D. shall 3.--I heard they went skiing in the mountains last winter. --It ____ true because there was little snow there. A. may not be B. won’t be C. couldn’t be D. mustn’t be 　 情态动词 表示推测 不表示推测 can could may might shall should must will would ought to have to dare (daren’t) need (needn’t) used to Main Points: The thirteen modal auxiliaries: can / could, may / might, will / would, shall / should, must, need, dare, ought to, used to B. Features of modal auxiliaries: 1. Morphologically: no non-finite forms nor -s forms 2. Syntactically: initial in a finite verb phrase and followed by a bare infinitive 3. Semantically: a. with lexical meaning b. no co-occurrence of two modals in a verb phrase c. not necessarily markers of time reference d. polysemous (多义) 可兼做行为动词的情态动词：need 、 dare 情态动词 (+动词原形) 行为动词 . need dare 1.无人称和数的变化; 2.尤其用于： *否定句及疑问句中; *在if/whether之后; *或与hardly, never, no one, nobody连用; 3.常以needn’t 和daren’t 的形式出现; 4.dare有其过去时dared. 多用于肯定句; (sb.) need to do dare to do (sth.) need to be done (sth.) need doing 判断正误: How dare you say such a thing? How dare you to say such a thing? He daren’t to speak English before such a crowd, did he? He daren’t speak English before such a crowd, dare he? Nobody need to be afraid of catching the disease. Nobody need be afraid of catching the disease. These dishes need be cleaned carefully. These dishes need to be cleaned carefully. These dishes need cleaning carefully. 注意对need问句的回答: --Need